Carrier recombination mechanism in CsPbBr3 revealed by time-resolved photoluminescence spectroscopy

We systematically investigate the recombination mechanism of photogenerated charge carriers in bulk $\mathrm{CsPbB}{\mathrm{r}}_{3}$ by means of time-resolved photoluminescence (TR-PL) spectroscopy at low temperature and various laser excitation powers. A dynamic recombination model is proposed to describe the TR-PL that predicts the time-dependent exciton and free-charge populations. It provides a clear representation of competing mono- and bimolecular recombination processes. A decrease in carrier lifetime with increasing laser intensity was observed that was attributed to exciton-exciton scattering. A bimolecular recombination coefficient of $\ensuremath{\sim}{10}^{\ensuremath{-}7}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{3}/\mathrm{s}$ was obtained for exciton recombination. As the concentration of photoexcited carriers increases, stronger exciton-exciton annihilation occurs. The exciton-exciton annihilation rate for $\mathrm{CsPbB}{\mathrm{r}}_{3}$ is $3.63\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{3}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ at 10-mW laser power. Notably, the exciton-exciton annihilation rate in bulk material is comparable to that obtained for photoexcited $\mathrm{CsPbB}{\mathrm{r}}_{3}$ nanoscale quantum dots.